This invention relates to the field of object location and tracking systems for asset management systems, and more particularly, this invention relates to object tracking and location systems using a plurality of tag signal readers contained within a monitored environment and using differentiation of first-to-arrive signals to locate a tag applied to an object.
In U.S. Pat. Nos. 5,920,287; 5,995,046; 6,121,926; and 6,127,976, the disclosures which are hereby incorporated by reference in their entirety, a real time location system is disclosed using a plurality of tag emission (signal) readers that are disbursed throughout a monitored environment, such as a manufacturing environment, and are operative with a location processor to determine which tag signals are first-to-arrive signals and conduct differentiation of the first-to-arrive signals to locate a tag located within the monitored environment. In this system architecture arrangement, the tag signal readers are connected in a xe2x80x9chub and spokexe2x80x9d arrangement. For example, a tag signal reader could include two antenna for diversity that receive power from the location processor and connect in the xe2x80x9chub and spokexe2x80x9d arrangement to a location processor, allowing eight tag signal readers to connect to one location processor. In some environments, where the cable line length spacing among the different tag signal readers could be many hundreds of feet, the cabling costs could exceed the hardware costs.
In a multistory building or other building, such a xe2x80x9chub and spokexe2x80x9d arrangement may not be necessary, and an alternative architecture could be preferable that would have lower costs, as long as it provided the ability for any connected location processor to determine which tag signals are first-to-arrive signals and conduct differentiation of first-to-arrive signals to locate a tag connected to the object to be located.
The present invention provides a location sensor array architecture using a single coaxial line for removing delay, and in one aspect, time and multiplexing techniques, which significant cost savings for certain applications, such as multistory or small buildings. Multiple location antennae correspond to tag signal readers and are connected by a common connection cable as a coaxial cable and processed by a location processor as a preferred one (dual channel) processor. Tag signals received by any antenna of a tag signal reader are timed and associated with that particular receiving antenna and tag signal reader, such as using timed, multiplexing techniques.
The system of the present invention identifies objects within a monitored environment and includes a plurality of tag signal readers contained within the monitored environment and serially connected along a single connection line for receiving tag signals from at least one tag contained within the monitored environment. The tag signals received by tag signal readers are timed and associated with a particular tag signal reader. A location processor is connected to the single connection line for determining which tag signals are first-to-arrive signals and conducting differentiation of the first-to-arrive signals to locate a tag. Although different types of location processors could be used, typically a single processor could be sufficient.
In yet another aspect of the present invention, the single, connection line comprises a single, coaxial cable. The tag signals are pseudorandom spread spectrum radio frequency signals. The location processor comprises a matched filter correlator having a plurality of matched filter banks containing parallel correlators. The tag comprises a mobile device.
In yet another aspect of the present invention, the system identifies tagged objects located within a multistory building. A plurality of vertically separated tag signal readers are positioned respectively at a corner on each floor of the multistory building and serially connected along a single connection line as a coaxial cable extending vertically and connecting tag signal readers at the corners. Tag signals are received from at least one tag contained within the multistory building. The tag signal is received by tag signal readers and associated with a particular tag signal reader at a corner. The location processor is connected to the signal connection line and determines which tag signals are first-to-arrive signals and conducts differentiation of the first-to-arrive signals to locate a tag within the multistory building.